The present application relates to the field of imaging, and in particular computed tomography (CT) imaging where volumetric data of an object under examination is generated. It finds particular utility in medical applications, and in particular in medical applications where it is desirable to generate a tilted image(s) and/or to generate targeted images representative of a targeted field of view. However, it may also find utility in security and/or industrial applications, where images are developed based upon detected radiation (e.g., such as detected X-ray radiation and/or gamma radiation).
CT imaging modalities are useful to provide information, or images, of interior aspects of an object under examination. Generally, the object is exposed to radiation photons (e.g., such as X-rays, gamma rays, etc.), and an image(s) is formed based upon the radiation absorbed and/or attenuated by the interior aspects of the object, or rather an amount of photons that is able to pass through the object. Traditionally, the image(s) that is formed from the radiation exposure is a density image or attenuation image, meaning the image is colored/shaded as a function of the respective densities of sub-objects comprised within the object under examination. For example, highly dense sub-objects absorb and/or attenuate more radiation than less dense sub-objects, and thus a sub-object having a higher density, such as a bone or metal, for example, will be shaded differently than less dense sub-objects, such as muscle or clothing. However, more recently, multi-energy imaging systems (e.g., such as dual-energy CT scanners) have been utilized to discriminate sub-objects based upon more than density. Such systems are typically configured to distinguish sub-objects based upon density and other physical characteristics, such as atomic number, for example.
In a CT imaging modality, data generated from the detected radiation is generally reconstructed to form a plurality of image slices that, when combined, form a three-dimensional image of the object under examination. As will be further described below with respect to FIG. 3, image slices generated from detected radiation are typically perpendicular to a longitudinal axis of the object (e.g., the image slices are substantially parallel to one another and spaced in a z-direction parallel to an axis of rotation for the CT). However, in some diagnostic applications, it is desirable to generate image slices at a non-perpendicular orientation to better visualize certain structures within the object. For example, image slices at angles other than 90 degrees relative to the longitudinal axis of the object (e.g., non-transverse image slices) may be desirable when studying certain organs (e.g., the eyes).
Conventionally, a rotating gantry of the CT (e.g., to which the radiation source(s) and the detector array are attached) is mechanically tilted prior to the examination of an object to provide for such non-perpendicular orientations. That is, the rotating gantry may be tilted about a pivot point so that the rotating gantry may be positioned at different tilt angles (e.g., so that the axis of rotation of the gantry is inclined relative to the longitudinal axis of the object). More recently, in an effort to, among other things, reduce cost and complexity associated with the mechanical tilt design, techniques for reconstructing tilted images from volumetric data acquired from a non-tilted gantry (e.g., where the axis of rotation is substantially parallel to the longitudinal axis of object) have been proposed. In this way, the tilted images are created during image reconstruction as opposed to being created as a function of the tilt angle of the rotating gantry, for example.
While a digital tilt feature has numerous benefits over the mechanical tilt design, there are some drawbacks. For example, merely a fraction (e.g., 50%) of the portion of the object exposed to radiation may be represented in a digitally tilted image, and thus more radiation may be used than is necessary.